>> Going further into Wonderland, at "today's prices," what might a buyer expect to pay a coin broker for a bag of 90%ers? If one were the seller of such a bog to a dealer or broker who must make a profit, what might be received? I know it's all speculation but...... <<

Except for silver dollars (which have more silver per dollar of face value), 90% silver US coinage has about 0.72 ounces of silver. So you can multiply the current silver price by 0.72 to get a good idea of the value.

With silver at $37 per ounce that means a dollar of silver coins (except silver dollars again) would have about $27 in silver value. A typical bid/ask spread might be something like $25 to buy and $29 to sell, give or take a little. Large brokers doing a very high volume might have somewhat tighter spreads than a typical dealer, though -- it's the old saying "we make up for it in volume"...